<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let aa;
        aa=10;
        console.log(typeof aa);
        aa="11";
        console.log(typeof aa);
        aa=true;
        console.log(typeof aa);

        let bb;
        bb="10";
        let cc;
        cc=10;
        console.log("bb==cc:"+(bb==cc));
        console.log("bb===cc:"+(bb===cc));

        let arr=[];
        arr[0]="2233";
        console.log(arr[0]);
        arr[1]=12;
        console.log(arr);
        arr.splice(0,2);
        console.log(arr);

        let sum=function(x,y){
            console.log(x+y);
        }

        sum(10,20);
    </script>
</body>
</html>